B E Prather1,
M A Chapin1,
J V Hinchey1
(1) Shell International Exploration and Production, Rijswijk, Netherlands
Abstract: Role of shallow analogs in exploration and production of turbidite reservoirs
The high frequency content of shallow seismic allows display of near seafloor morphology and geologic features. Shallow analogs have a variety of uses throughout the life cycle of typical deepwater plays, including: 1) drilling hazard identification 2) slope depositional process modeling, 3) architecture calibration of seismic facies, and 4) reservoir modeling.
Rendered images of the seabed from 3D seismic data supplement and/or replace high-resolution 2D site surveys for identifying shallow hazards. These seafloor images also provide insights into active depositional processes such as slumps, mud volcanoes, erosional scours, channel morphology, and levee formation.
Detailed mapping of shallow, well-imaged seismic sequences improve our understanding of deep-water depositional process models. Patterns of deposition controlled by slope gradient, entry points and accommodation space are most confidently identified in the near-seafloor setting. Near-seafloor features where these controls persist through multiple depositional episodes make particularly useful analogs for deeper sequences. Variable acoustic rock properties in most near-seafloor settings, however, require drilling for reliable lithologic calibration.
Although near-seafloor analogs have less resolution than outcrops, they provide 3D information typically lacking from outcrops. Near-seafloor seismic image surfaces related to episodes of starvation, bypass and/or erosion that control both reservoir bed-length and connectivity. Outcrops show us that these surfaces are too large to be easily detected with wireline tools and too small to be confidently mapped with conventional seismic. Dimensional data such as channel width, thickness, sinuosity, meaderbelt width, and areal extent of slumps from images of shallow analogs, can be applied to reservoir models where appropriate.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana